What Killed Off the Dinosaurs?

The Atlantic has an article about the cause of the dinosaur extinction at the end of the Cretaceous Period, 66 million years ago and the raucous debate within geological circles.  Overall it’s a pretty good article, mostly addressed to laymen, and doesn’t get too scientific.  And let’s face it, dinosaurs are darn interesting—they’re big (the apatosaurus were the biggest land animal ever to walk the earth), scary (who didn’t shudder at the T-Rex scene in Jurassic Park), and have captivated imaginations since… well since we figured out what those skeletons represented.  I remember, as a child, my father taking me to the Chicago Museum of Natural History and standing in front of the T-Rex display—utterly fascinated—its part of the reason I am a geologist.

And they’re all gone (except for birds, but that is a post for another time)—long gone—disappointingly gone—so much so that the rumors of a dinosaur surviving still circulate: mokele-mbembe anyone?   The Atlantic casts the debate among geologists (not pseudo-geologists that think dinos died in Noah’s flood) as a David-Goliath battle (speaking of the Bible) between plucky Gerta Keller and her small merry band of volcanists and the disciples (minions?) of Luis Alvarez, the IMPACTERS (duh, duh, duh, duuuuuhhhh).  Sorry, but I’m only moderately exaggerating the melodrama the Atlantic article tries to make of the dispute.

As the article says:

Before the asteroid hypothesis took hold, researchers had proposed other, similarly bizarre explanations for the dinosaurs’ demise: gluttony, protracted food poisoning, terminal chastity, acute stupidity, even Paleo-weltschmerz—death by boredom. These theories fell by the wayside when, in 1980, the Nobel Prize–winning physicist Luis Alvarez and three colleagues from UC Berkeley announced a discovery in the journal Science. They had found iridium—a hard, silver-gray element that lurks in the bowels of planets, including ours—deposited all over the world at approximately the same time that, according to the fossil record, creatures were dying en masse. Mystery solved: An asteroid had crashed into the Earth, spewing iridium and pulverized rock dust around the globe and wiping out most life forms.

Keller, a 73-year-old paleontology and geology professor at Princeton University, instead has proposed that a major volcanic eruption in Western India in the area known as the Deccan Traps was responsible for the disappearance, some 66 million years ago, of the dinosaurs.  The Atlantic paints the dispute as nasty and vicious—with geologists on both sides hurling insults and trying to ruin each other’s academic careers.

It all makes for a fine story, well told by the Atlantic writer, and captivating to read.  I have a few observations I’d like to make.

Observation #1:  This is no way to conduct scientific debate, and I think there is an undercurrent of smug satisfaction by the Atlantic writer that scientists are just like everybody else—prideful, petty, turf-protecting, and sometimes just downright mean.  Why this seems to come as a surprise to anybody is a surprise to me.  Scientists are human and can be counted on to act like… well… humans.  There does seem to be a certain schadenfreude in the Atlantic’s tone that the scientists are acting like… uh… politicians, but to be fair to the Atlantic, a lot of science these days does seem to be politicized.  Also, to a large extent, this debate takes place in academia, and like a dear late friend of mine who was a university professor often told me, academia has THE pettiest politics of anything including politics. Still, I’m an old-fashioned guy, so I have to say to the parties in this debate: knock it off—you’re making us geologists look bad, you should be ashamed of yourselves.  There is no excuse for anybody to call Gerta Keller a bitch, none whatsoever!

Observation #2:  No event of historical geology can ever be proved.  It is all inductive reasoning of the remaining physical evidence to the most probable conclusion.  To quote from the article:

The impact theory provided an elegant solution to a prehistoric puzzle, and its steady march from hypothesis to fact offered a heartwarming story about the integrity of the scientific method. “This is nearly as close to a certainty as one can get in science,” a planetary-science professor told Time magazine in an article on the crater’s discovery. In the years since, impacters say they have come even closer to total certainty. “I would argue that the hypothesis has reached the level of the evolution hypothesis,” says Sean Gulick, a research professor at the University of Texas at Austin who studies the Chicxulub crater. “We have it nailed down, the case is closed,” Buck Sharpton, a geologist and scientist emeritus at the Lunar and Planetary Institute, has said.

Really, this is so disappointing if these guys are being quoted accurately—they are talking like idiots.  They really should know better than to make statements like “nearly as close to a certainty” and “case closed”.  The case is NEVER closed.  More evidence is discovered and the explanation MUST be changed.  The conclusions of science are always provisional, especially about events in the distant past.

Observation #3:  Neither cause being advocated for is necessarily an “either-or” situation.  There is no reason it couldn’t be “both-and”.  The article notes this:

Some scientists have attempted to find a middle ground between the two camps. A team at UC Berkeley, headed by Renne, has recently incorporated volcanism into the asteroid theory, proposing that Chicxulub’s collision unleashed earthquakes that in turn triggered Deccan’s most destructive pulses. But Keller rejects this hypothesis. “It’s impossible,” she told me. “They are trying to save the impact theory by modifying it.”

But then seems to pooh-pooh it, as if “you had better pick a side and stick to it”.  That is ridiculous, and Keller does herself a disservice by rejecting the “both-and” hypothesis.  Modifying a theory based on new evidence is what scientists SHOULD do.  I will go out on a limb here, and make a prediction—the continual gathering of evidence will eventually support a “both-and” hypothesis.  The critical issue, you might have noted, is really timing.  What was the timeline of the extinction event?  When did it begin, when did it accelerate, and when did it end?  How close can you correlate the asteroids impact to the extinction event?  How close can you correlate the volcanic eruptions to the extinction event?  Keller thinks she has evidence the asteroid hit 200,000 years before the extinction event started, while recent work by Renne places the impact within 32,000 years.  Please note that a 5% error bar, very reasonable for this type of work, is 3,300,000 years for 66 million years.  Maybe Klasie could weigh in on that remarkably high precision geochronology of ⁴⁰Ar/³⁹Ar dating, I don’t have the chops to critique it.

It has been pretty well established there have been 5 mass extinction events in the earth’s past.  They were:

1. 445 Million Years Ago – End of the Ordovician Period – 57% of all genera – most likely culprit: climate change.
2. 370 Million Years Ago – Late Devonian Period – 70% of all marine species died off – oxygen depletion and global cooling.
3. 250 Million Years Ago – End of the Permian Period – the worst, some estimate 96% of all species died out – super volcanos in Siberia the main cause.
4. 200 Million Years Ago – End of the Triassic Period – 1/5th of all families of marine life were killed – most likely cause the eruption of the Central Atlantic magmatic province.
5. 66 Million Years Ago – End of the Cretaceous Period – 76% of all living things on Earth- big rock from space and/or super volcanos in India.

The Atlantic plays up the idea, embraced by Keller, that we are at the beginning of the 6^th Extinction Event, this one man-made.  It’s an intriguing idea, because, aside from climate change, some 322 species have gone extinct in the last 500 years due to man, with two-thirds of those occurring in the last two centuries due to habitat loss or over-hunting/fishing.  According to a review published on May 29 in the journal Science, current extinction rates are up to a thousand times higher than they would be if people weren’t in the picture.  So, how about it, are we going to be the cause of our own demise?  Are we ourselves, the four horseman of the apocalypse?  Would God permit us to destroy ourselves?  After all, it would the SIXTH extinction, six being the number of a man (Revelation 13:18).